HOME |
private-list |
private-modify |
© |
Weather, Seasons of the Year
- Read the weather forecast:
Today and Tomorrow There will be sunny intervals and scattered showers. Most of the showers will be across Northern Ireland, Scotland and parts of northwest England, some heavy. Elsewhere, staying mostly dry. Warm in the east.
Today night Many inland areas becoming dry with clear spells developing. Rather cloudy in the north and west, with showers continuing to affect coasts and hills exposed to the northwesterly breeze.
Outlook On Saturday, Scotland will be cloudy with the odd shower. Elsewhere, starting generally dry with sunny spells. Cloud forming, with showers developing, these mostly in east, where heavy. Warm in sunnier spots, near normal elsewhere. On Sunday, many areas starting cloudy. Outbreaks of rain affecting northern parts of Scotland, with drizzle near western coasts elsewhere. Bright or sunny spells developing inland. Mostly warm, perhaps very warm in sunnier spots.
- Do you understand the weather words? Explain the meaning.
Clear and bright, Sunny, Partly cloudy, White medium level cloud, Sunny intervals, Dark and Rainy, Black low level cloud, Light rain shower, Drizzle, Heavy rain shower, Hail and snow, Cloudy with sleet, Sleet shower, Light snow shower, Cloudy with heavy snow, Thunder, Mist, Fog, Hazy, Blizzard - Combine some of the terms with the pictures.
- Make out your own weather forecast for today and tomorrow. Use the words from above.
Weather and Climate New Englanders have a saying
'If you don't like the weather, just wait a minute.'. We're accustomed to thinking of our climate as stable.
Weather is dynamic and seen on a geologic scale,
climate is no more stable than weather. They are products of interacting forces we are only beginning to understand. Much in our lives depends on weather and climate and our actions can have marked effects on them. We can't control
natural events, but we can study the
processes that drive our climate and weather systems. We can strive to understand Earth's complex systems of air, water, and life, and we can learn how our actions fit into the puzzle of weather and climate.
Layers of the Atmosphere Separating Earth from inhospitable
chilly space is a 500-mile-thick cocoon of gases called
the atmosphere. It
keeps our planet warm and protects us from the direct effects of
the Sun's radiation. Without this regulation, Earth could not
sustain life. The atmosphere is made up of several
layers. Extending up to 10 miles above Earth's surface, most of the
clouds you see in the sky are found in
the troposphere, the layer of the atmosphere we associate with weather. It contains a variety of gases, made up primarily of
nitrogen and
oxygen, plus
water vapor, carbon dioxide, methane, nitrous oxide, and others.
The stratosphere extends from about 10 to 30 miles above the surface of Earth and includes the
ozone layer. Ozone molecules concentrated here protect us from the Sun's
harmful effects. Thirty to 50 miles above the surface is
the mesosphere, the coldest part of the atmosphere. Above the mesosphere, in a layer called
the ionosphere (or the thermosphere) about 50 to 180 miles from the surface, temperatures reach up to several thousand degrees. Beyond the ionosphere there is
the exosphere, the outermost layer and transition zone into space, which extends to roughly 500 miles above the surface of Earth.
Greenhouse Effect The gases that help
retain heat are called
greenhouse gases. These gases, primarily
carbon dioxide, absorb heat instead of allowing it to escape into space. This 'greenhouse effect' makes the planet a hospitable place. However, it can have negative effects, too. Since the 1800s, industrialized societies have burned
fossil fuels such as coal, oil, and natural gas; these processes all give off carbon dioxide. With more of it in the atmosphere, more heat is retained, causing a global temperature increase. Even a few
degrees can have serious consequences.
Tropical diseases could increase, since mosquitoes and other disease-carrying insects thrive in a warmer climate.
Sea levels could rise. Prosperous farmland could dry up and agricultural regions could shift, wreaking havoc on the global economy. It is possible that the recent
warming trend is due more to natural cycles of cooling and warming than to human activity. Global climate change occurs on a scale of tens or hundreds of thousands of years, but scientists have only begun to study these effects in the last 150 years. Still, most of them agree that we affect the climate. Just how much we can influence it remains to be seen.
The Hole in the Ozone Layer Though its effects on our weather might be small, the
ozone concentrated in the stratosphere is crucial to
a hospitable climate as it helps protect us from
damaging ultraviolet radiation from the Sun which causes cancer and weakens our immune systems. Ozone is created when oxygen molecules are split by ultraviolet radiation into two separate oxygen atoms that collide with oxygen molecules to form ozone. Scientists believe that ozone is being destroyed as a result of some industrial activities: specifically, the use of
chlorofluorocarbons (CFCs), man-made chemicals used in
refrigeration.
Ozone depletion is most severe in the polar regions, particularly over Antarctica. Though most countries have banned or pledged to discontinue the use of ozone-depleting substances, their effects may continue to be felt for a number of years. CFCs linger in the troposphere for years before reaching the ozone layer. It is believed that within the next few decades ozone depletion from CFCs will
peak and then gradually dissipate.
Clouds in the Sky Earth was formed 4.6 billion years ago with no water at the start. 3.8 billion years ago, water vapor began to form in the atmosphere, oceans formed and the continuous process of precipitation and evaporation called
the hydrologic cycle began. Today
the oceans cover 70 percent of Earth and distribute heat around the planet keeping heat and cold circulating by way of
surface currents. Only less than one percent of all is
groundwater which can be used as
drinking water. As
water evaporates from the oceans, it enters the atmosphere and
forms clouds. When enough water or ice collects in a cloud, it
rains or
snows. There are many kinds of clouds and each signals a different kind of weather. Wispy-and-thin-looking
cirrus clouds, for example, are high up in the troposphere. Though they are composed of ice, they are usually associated with pleasant weather.
Stratus clouds, which form in lower parts of the troposphere, consist of water droplets, cover most of the sky with
an even, gray color similar to a fog and, as well as
cumulus, nimbostratus, and other cloud types, signal light rain.
Cumulonimbus clouds are tall, dense clouds shaped like a block or anvil. They
signal thunderstorms and also spawn tornadoes, as well as other violent weather effects such as
hail.
Thunderstorms and Tornadoes At any given moment, an estimated 2,000
thunderstorms are in progress. These storms vary from mild rainstorms to very damaging storms featuring hail and high wind. Thunderstorms form when warm air moves quickly upwards from Earth's surface into the colder levels of the atmosphere. The result is
rain, wind, lightning, and thunder. Lightning forms when updrafts of air carry water droplets, which have
a charge, upward to heights where some freeze into ice particles and form a cloud. As these particles begin to fall back to Earth, charges within the cloud become mixed and the differences are released as lightning. The noise accompanying lightning is called
thunder. You'll normally hear it a few moments after you see the sky light up. Light travels faster than sound, so if you are at a distance from the storm, lightning and thunder seem oddly disconnected. In some thunderstorms, an unstable
column of warm air rising within cumulus clouds can start to rotate. If conditions are right,
updrafts alter the air's rotation from horizontal to vertical, and the funnel forms, which can extend to the ground, forming
a tornado. Tornadoes are typically found on land, range from a few feet to one mile in diameter and are short in duration. Though relatively small and localized, they can be
extremely violent. The
wind speed inside a tornado can exceed 200 miles per hour, enough to turn everyday objects into deadly projectiles. Tornadoes occur all over the world but they are most common in the midwestern United States.
Tropical Storms, Hurricanes and Typhoons In 1998, Mitch, the deadliest hurricane in the last 200 years, ripped through Central America, killing more than 11,000 people and leaving millions homeless. In Nicaragua,
mudslides buried whole villages.
Hurricanes are large storms coming from June to November in the central Atlantic. They can cover thousands of miles drawing their strength from the warm tropical waters of the ocean. At the beginning, the energy is converted into thunderstorms that gathering together begin to rotate in the same direction, forming
a spiral with an eye in its center, a system called
a tropical depression. Tropical depressions with slower wind speeds are called
tropical storms. As a tropical storm spins and gains power, it becomes a hurricane. Its winds can tear roofs off of houses and heavy rain can ruin crops, cause flash flooding, and spark deadly landslides. Hurricanes and tropical storms are ranked on the Saffir-Simpson Hurricane Scale, which takes into account their wind speed and pressure, and are given names. Each year, meteorologists come up with an alphabetical list of names. Once on land, hurricanes
gradually dissipate. While hurricanes batter the Americas, similar storms are found in other parts of the world. In the Pacific and Indian Oceans
typhoons wreak havoc in coastal areas. On average, these storms are much more destructive and frequent than hurricanes, since they can travel for much longer over warm Pacific waters than they can over the cold waters of the Atlantic.
Snow, Glaciers, and Ice Ages How does
snow form? In the atmosphere water condenses into a tiny droplet. Cold air freezes it into an ice crystal with a unique shape depending on the surrounding temperature and water vapor content. Increasingly heavy, the crystal falls, leaving the cloud. As it descends, it can come into contact with warmer air that makes it melt somewhat which acts like a glue, causing crystals to bond together into larger
snowflakes. If the crystals melt too much and then refreeze, there is sleet instead of snow. Once on the ground, snow can remain if it is cold enough to keep it from melting.
Glaciers are made up of snow that accumulates and eventually turns to ice. In the 1930s, a Serbian mathematician named Milutin Milankovitch theorized that global climate changes are brought about by regular changes in
Earth's axis, tilt, and orbit. Earth doesn't rotate perfectly like a wheel; it spins like a wobbling top causing a slight change every 22,000 years. Every 100,000 years, Earth's orbit becomes more elliptical, taking Earth farther from the Sun. And finally, every 41,000 years the tilt of the axis changes. Thus, at certain times there is less sunshine hitting Earth and snow begins to accumulate. Snow reflects some sunlight back into space, which contributes to cooling. Temperatures drop, and glaciers advance. Not all
ice ages occur on a 100,000-year scale. One called the Little Ice Age lasted from about 1400 to 1800 and though its effects were fairly mild, for those who watched glaciers advance, it was certainly dramatic. During the last 10 million years, Earth has had 10 major ice ages, each followed by a warm period of about 10,000 years. It seems we're at the end of one warm period. Should we expect another major ice age soon? There's no way of knowing. Climate remains difficult to predict.
Weather Forecasting Weather predictions are essential for farmers to plan the planting and harvesting of their crops, or airlines, which need information about
local weather conditions in order to schedule flights. Modern meteorlogists involve a variety of tools: thermometers measure air temperature, anemometers gauge wind speeds, and barometers provide information on air pressure. These instruments allow to gather data about what is happening near Earth's surface. Today, data from other parts of the atmosphere helps to create a more descriptive picture. Doppler radar measures reflected sound waves broadcast from an antennae. If the waves come into contact with objects in their path, such as dust particles or ice crystals, they are reflected back. For viewing weather on a worldwide scale, satellites are invaluable. Satellite data is gathered by two types of sensors. The camera-like "imager" works by capturing visible light to create images where different surface features reflect light in distinctive ways that can be distinguished from each other. The "sounder" is an infrared sensor reading temperatures and can be used any time, including night. The higher the temperature of the object, the more energy it emits. Using all these methods, reasonably accurate forecasts can be made up to about five days in advance. Beyond that, detailed forecasts are less useful. Finally, the most basic weather forecasting consists of simple observation. "Red skies in morning, sailor take warning; red skies at night, sailor's delight." A red Sun can presage rain, since it occurs when the air is full of dust and water vapor.
From:
http://www.bbc.co.uk/weather/ukweather/ http://www.learner.org/exhibits/weather/ http://www.bbc.co.uk/weather/bbcweather/features/symbols.shtml